Semiconductor components are typically subjected to a comprehensive functional test after their production. By way of example, the functional test for a dynamic random access memory comprises writing data to individual memory cells, reading out the data from the memory cells and comparing the written and read-out data. In order to carry out the functional test, the semiconductor component is connected to a tester with numerous channels for inputting and outputting signals. By way of example, a plurality of semiconductor components may in each case have a number of 64 connection contacts and the tester may have a number of 1024 channels. In this case, up to 16 of the semiconductor components can be connected to the tester.
The tester typically comprises a central unit (tester mainframe) and a component-specific adapter (HiFix). The central unit comprises, for example, the power supply, a programmable control unit for defining signal patterns, signal generators for generating output signals on the channels, signal detectors for detecting input signals via the channels, for example comparators for comparing voltage levels, oscilloscopes for representing input or output signals, and a standardized measuring head (test head) for inputting and outputting signals. The component-specific adapter comprises connection receptacles for a plurality of semiconductor components and connections for the standardized measuring head of the central unit. The component-specific adapter thus forms an interface between the central unit and generally a plurality of semiconductor components.
Since the clock frequencies and switching speeds of semiconductor components are constantly increasing, the requirements made of the measurement accuracy of a tester are also constantly increasing. In general, testers are therefore characterized with regard to their electrical properties both after purchase and during use in production. By way of example, the electrical properties of an individual signal driver can be determined by using an oscilloscope to graphically represent an output signal generated by the signal driver. In order to connect the oscilloscope, however, the arrangement has to be altered. Therefore, this method for characterizing an individual channel of the tester cannot be employed under production conditions. It is also possible to determine the electrical properties of a signal driver using a signal detector of the same channel. However, no semiconductor component is connected to the tester, so that the electrical properties determined by the characterization do not describe the signal path occurring under production conditions. The different sections of the signal path from the tester via the component-specific adapter to the semiconductor component can also be characterized independently of one another with regard to their electrical properties. In this case, however, the connection conditions that are predetermined by the remaining sections of the signal path under production conditions are disregarded in each case. In particular, the influence of the housing of a semiconductor component is not taken into account. Therefore, the electrical properties of the signal path present under production conditions cannot be determined by characterization of the individual sections.
To summarize, it can be stated that the characterization of testers according to the prior art does not include the entire signal path between the semiconductor component to be tested and the tester such as is present under production conditions.